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Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/5/2009 Publication Date: 8/19/2009 Citation: Eujayl, I.A., Strausbaugh, C.A. 2009. Evaluation of sugar beet germplasm and plant introductions response to rhizomania and storability in Idaho, 2008. Plant Disease Management Reports. 3:FC105. Interpretive Summary: Breeding lines, advanced germplasm, sea beet and wild-relatives accessions of sugarbeet were evaluated for response to rhizomania in a grower’s field with history of high level of the disease. The objectives of this study were to identify germplasm and accessions that carry novel resistance to the disease and utilize these lines in the breeding program. Mature roots from the experimental plots were scored for rhizomania severity, as well as evaluated for storability performance in an indoor commercial sugar beet storage facility set to hold at 35°F for 90 days. As a result of this screening, we identified new accessions from sea beet and wild Beta species that carry resistance genes and performed similarly to resistant checks. These accessions will be studied at the molecular level to verify if they provide new resistance genes. The variation within these accessions could be of genetic value in breeding for resistance to rhizomania. Additionally, some germplasm lines showed both rhizomania resistance and a significantly lower damage (fungal growth) during storage. The relationship between rhizomania resistance and fungal growth is apparently complex as shown in contrasting performances of some accessions. Technical Abstract: The sugar beet industry requires that all cultivars must posse’s high level of genetic resistance to rhizomania. The objectives of this research were to identify germplasm and accessions that carry novel resistance genes so as to be utilized in the breeding program. Sixteen accessions and checks were evaluated in a grower’s field highly infested with rhizomania virus. Mature roots were evaluated using a scale of 0 to 9 (0 = healthy and 9 = dead). The checks responded as expected for US75 (susceptible), Beta 4430R (Rz1 resistant check), and Angelina (Rz1+ Rz2 resistant check). Several entries were susceptible and were not significantly different from the susceptible check. Accessions; K0848 (Beta v. maritima) and K0843 (Beta webbiana) were evaluated for the first time in the field and performed similar to the Rz1 and Rz1+Rz2 resistant checks, respectively. The storability rating based on the percentage of root surface area covered with fungal growth (Basidiomycetes) is not directly correlated to disease severity index, as evident in the susceptible or the resistant checks. In previous studies fungal growth was found to be correlated with sucrose loss. In this study accession KC4931 showed both rhizomania resistance and a significantly lower percentage area covered with fungal growth. The relationship between rhizomania resistance and fungal growth is apparently complex as shown in the performance of entries KC4931and KC1036. |
